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In its first generation, IMA could not power the car on electricity alone, and could only use the motor to assist or start the engine. The 2006 Civic Hybrid, however, can activate the electric motor while the vehicle is coasting without turning the internal combustion engine on, though in contrast to Toyota's Hybrid Synergy Drive (HSD) or General Motors and DaimlerChrysler's Global Hybrid Cooperation, the IMA has a less powerful motor/generator which allows the car to slow or stop its rate of deceleration to a lesser extent; it cannot operate without turning over the engine which is directly coupled to its electric motor.

The theory behind IMA is to use regenerative braking to recapture some of the energy lost through deceleration, and reuse that energy later on to help accelerate the vehicle. This has two effects: it increases the rate of acceleration, and it reduces the work required of the petrol engine. The acceleration boost is important as it allows the engine to be scaled down to a smaller but more fuel-efficient variant without rendering the vehicle overly slow or weak. This smaller engine is the primary reason cars equipped with IMA get better highway mileage than their more conventional counterparts.

Additionally, vehicles equipped with IMA can shut off their engine when the vehicle stops and use the electric motor to rapidly spin it back up when the driver releases the brake pedal. They also have a conventional starter as a backup, making it the only production hybrid system which can operate with its high voltage electric system disabled, using only its engine like a traditional vehicle. However, since the IMA also acts as the vehicle's alternator, eventually the 12 volt accessory battery would require an external charge